Research On Flexural Behavior Of New Composite Beam

Though the precast beam with traditional rectangular cross-section has largestiffness, the beam has some disadvantages, such as heavy self weight and poorintegrity of the beam-column joints. Our research group proposed a new type ofcomposite beam in2004, the cross-section of the precast component is U-shaped orinversed T-shaped. Though it overcomes the disadvantages of traditional compositebeams, the precast beam needs a lot of supports during construction due to poorbending stiffness and it’s easily damaged during transportation and storage.Therefore, the present study proposed a new type of precast beam with U-shapedgroove in the ends and rectangular cross-section in the middle. In addition, the stressperformance of the section at the end of frame beam significantly affects the safety ofthe structure and the potential plastic hinge region exists at the end of frame beam.To this end, four full-scale specimens were tested under the monotonic loading inorder to study the flexural properties of the new composite beams. The test specimenconsists of two identical beams with one end supported on a stub casted integrallywith the two beam ends. Three beam types were compared, the new composite beam,the traditional rectangular cross-section composite beam and the cast-in-situ beam.The failure of the four specimens ultimately occurred with cross-section damageat the edge of the short column. Experimental results indicated that the assumption ofplane section was basically satisfied in the new composite beams before the beamscracking. The calculated values of the new composite specimen such as the ultimatebending moment, cracking moment, short-term stiffness before cracking,displacement ductility, and rotation capacity of the plastic hinge are slightly differentwith that of the cast-in-place specimen and much larger than that of the traditionalcomposite specimen. The results shows that the integrity, rigidity, and plasticdeformation capacity of the new composite beam-column joint are much bettercompared with the traditional composite beam-column joint. The cracking moment,ultimate bending moment, average crack interval, and short-term rigidity beforecracking based on the specification calculation agree well with the values calculatedbased on the present tests. The finite element analysis of the three types of specimenswas conducted through ABAQUS and the results are almost the same as as the testresults.